Counterpoint: Watchmen sucked terribly.
Nevermind how boring the movie was (which I personally found the graphic novel to slow for my tastes, so that could be a personal problem), he followed the exact plot of the source material without changing anything, except the ending. That single change completely undermines everything that came before it.
The Watchmen comic plot works because it posits this question of whether it is better to live with a lie that brings peace and unity to the world than to expose the truth and cause the probable end to the planet. Moore accomplishes this by having (fake) extra-dimensional beings blink into Earth causing the planet to have a common enemy/goal.
In Snyder’s version he replaces the extra-dimensional beings with Dr. Manhattan, a known U.S. Operative. Manhattan blowing up New York would not be a sufficient world event to cause permanent peace across the globe. This is a similar event to what happened in our real world when Chernobyl melted down. And we all know the world didn’t stop being a dangerous place afterwards (and in fact the comic was released after Chernobyl).